Question: Which of these numbers is composite? ${17,\ 19,\ 47,\ 49,\ 73}$
Explanation: A composite number is a number that has more than two factors (including 1 and itself). 17, 19, 47, and 73 each have only two factors. The factors of 49 are 1, 7, and 49. Thus, 49 is the composite number.